THE city’s relatively new system of grading schools, A to F, was meant in part to pressure them to improve – leading to higher scores among students. Has it worked?

A complete, definitive answer to that may not yet be known. But evidence we’re releasing today shows that sanctions for getting an F do indeed improve student proficiency. And that’s an encouraging sign.

Certainly, the practice of grading schools is one of the city’s most controversial. It’s intended to provide parents, teachers and the public valuable information about the quality of a particular school. Knowing that such indicators will be publicized, schools might be more motivated to produce better results.

But the progress-reports program introduced by Mayor Bloomberg and Chancellor Joel Klein has inflamed debate over school-accountability programs. Many worry that deeming a school as “failing” could cause it to get worse, not better, by crushing the morale of teachers and administrators.

Under the new policy, schools receive points on the basis of factors related to school environment, student proficiency and student academic progress. The point scores are then translated into letter grades. Bloomberg and Klein warned they would contemplate sanctions for some schools that got low grades.

The city used as a model similar programs in other large public-school systems, where research suggests these policies have been relatively effective. But there was little information on the impact of the New York program – so the debate over its effectiveness has occurred largely in a data vacuum.

In a new study for the Manhattan Institute, I analyzed student-level test scores in math and English to see whether student performance in schools with low grades actually improved. My study uses a powerful research procedure used to study similar accountability systems across the country: In essence, I compared the performance of students in schools that just barely received an F grade under the system to schools that just barely received a D grade. That way, I could measure the impact of the actual letter grade.

As it turned out, the dire predictions that the policy would harm struggling schools were unwarranted. Students in schools that earned an F or D at the end of 2006-07 made greater progress in math than students in schools that earned higher grades. (Students in F schools, however, did not make similar improvements in English.)

The positive results in math occurred even though schools only had a few months between when they received the grade and when students took the standardized exams.

Thus, the results show that being awarded an F has a meaningful, overall positive effect on low-performing schools. And, again – though the positive results might be smaller than some may have hoped – the system did not precipitate further declines, as critics had feared.

While these new data eliminate certain questions about the policy, many others remain unanswered.

For one thing, a system of assigning grades to schools should provide parents with reliable information about particular schools’ quality, but it isn’t clear that the current system does that well.

Also, while the results suggest that student math proficiency in F- and D-graded schools is improving somewhat faster than in schools with higher grades, my analysis doesn’t measure whether the policy has led to an improvement in New York schools more generally. These questions deserve further exploration.

Nevertheless, these early findings suggest that the progress-report program is having an overall beneficial effect on Gotham’s lowest-achieving schools. Critics can rest assured that this program, like other accountability reforms, has motivated schools to improve student achievement.

Marcus Winters is a Manhattan Institute senior fellow. His new study is titled, “Grading New York: An Evaluation of New York City’s Progress Reports Program.”